Traffic on the Bay Bridge (right, with the exclamation point) was light Tuesday morning in San Francisco, but side streets were backing up, as shown by Google Maps' new traffic feature.
Screenshot by Tom Krazit/CNET

Say goodbye to your favorite shortcuts.

Google Maps is adding traffic data for side streets this week, in addition to the data it already offers up for major highways. Major "arterial" roads, such as state highways or prominent boulevards in cities, will now have their own color-coded traffic information in Google Maps, giving drivers the option of selecting an alternate route based on current traffic conditions.

So how is Google expanding its traffic reports to side streets? If you're using Google Maps on your smartphone (with the notable exception of the iPhone, which doesn't support the feature, according to Google) you're automatically sending speed data back to Google wherever you go.

The trigger is the "My Location" button in Google Maps, which automatically signs you up for the traffic crowdsourcing program when that button is pressed. In addition, Palm Pre and MyTouch 3G users are automatically enrolled in the traffic crowdsourcing program.

You can opt out of the program, but at the expense of the My Location feature. Hit the "My Location" button again to figure out where you are in an unfamiliar city, and you're automatically re-enrolled in the program.

Traffic data has been available on major highways for years through Google Maps, but that data is collected from road sensors and private car fleets and is also available to dozens of third-party traffic providers. The number of people using GPS-enabled smartphones with Google Maps installed has dramatically increased since 2007, and many of them may not know that by using the My Location feature, they're also participating in a traffic-related survey.

Google took great pains to address the security and privacy concerns of the feature in the blog post announcing the new feature.

"We understand that many people would be concerned about telling the world how fast their car was moving if they also had to tell the world where they were going, so we built privacy protections in from the start," wrote Dave Barth, product manager for Google Maps. "We only use anonymous speed and location information to calculate traffic conditions, and only do so when you have chosen to enable location services on your phone."

Google also said it would delete the data it collects about the starting point and ending point of your journey as a natural course of the program: after all, it has to differentiate between someone stuck in traffic and someone parked outside the office.

Plenty of in-car navigation devices transmit real-time traffic information back to the mother ship, so it's not like Google's breaking new ground. But the popularity of Google Maps for cell phones means that Google has an edge in terms of the number of data points it can bring to the table.

About the author

Tom Krazit writes about the ever-expanding world of Google, as the most prominent company on the Internet defends its search juggernaut while expanding into nearly anything it thinks possible. He has previously written about Apple, the traditional PC industry, and chip companies. E-mail Tom.
See full bio